Multi-lumen catheters are used for the purpose of creating two or more separate fluid pathways, such as in hemodialysis applications. A primary goal of hemodialysis access is to provide a reliable and effective means of dialysis, which means that a sufficient volume of blood over a period of time must be removed from and returned to the patient. Because the contaminated and cleansed blood must be kept separate for an effective dialysis procedure, a dual lumen catheter is generally used. These dual lumen catheters are usually configured so that there is a shorter lumen that aspirates blood from a blood vessel of a patient to a dialysis machine where it is processed for the removal of toxins, and a longer lumen that infuses the purified blood to the patient. The shorter lumen utilized for aspiration is generally referred to as the “arterial lumen,” while the longer lumen utilized for infusion is generally referred to as the “venous lumen.” The reason for the different lengths is to minimize co-mingling of aspirated and infused blood.
The primary problems occurring in dual lumen dialysis catheters are blood clotting (thrombosis) and fibrin (the protein formed during normal blood clotting that is the essence of the clot) sheath formation. Thrombus and fibrin sheath formation can occlude distal tips of the dialysis catheter lumens, resulting in loss of catheter function when such an occlusion prevents blood flow. This typically occurs initially in the arterial lumen used for aspiration of blood from a patient. A secondary problem relates to the arterial lumen “sucking” against the vessel wall, in which the arterial lumen openings become fully occluded by the patient's vasculature.
To specifically address these problems, a new type of dialysis access catheter has been designed that utilizes independent “free floating” distal tip sections that separate at a distal end of the catheter to theoretically reduce the likelihood of potential occlusion and “sucking” during dialysis treatment. U.S. Pat. No. 6,001,079 to Pourchez and U.S. Pat. Nos. 5,947,953 and 6,190,349 to Ash et al., all incorporated by reference herein, are directed to said new type of catheter, hereinafter referred to as a “split-tip catheter.”
Catheters used for hemodialysis are generally inserted according to standard technique. This includes identifying the location of the central veins in which the catheter is to be inserted, utilizing the Seldinger technique to cannulate the central vein with a guidewire, and passing various instruments over the guidewire until the catheter is in place. In the case of a small diameter catheter made of relatively stiff material (i.e., a percutaneous catheter for acute access), the catheter itself can be passed over the guidewire and into the central vein. In the case of a larger diameter catheter, the passage to the central vein must be widened through the use of dilator(s), after which the catheter can be passed over the guidewire. Another possibility available to the physician is to use an introducer sheath, which is passed over the guidewire (after dilation or simultaneously therewith) forming a path for the catheter to access the central vein.
Due to the configuration of the split-tip catheter, standard insertion techniques must be modified. With respect to non-sheath insertions, the separate distal tip sections must each be passed over the guidewire to ensure their arrival at the targeted central vein without attendant problems. Suggested means for accomplishing this (in a dual lumen catheter) is to pass the back end of the guide wire through the distal end hole of one tip section and out a side hole thereof into the distal end hole of the other tip section (Patel et al., J. Vasc. Interv. Radiol. (2001), vol. 12, pages 376-378). However, such a method can become problematic depending on the placement of the side holes and, in fact, may be impossible in the event that no side holes are provided. With respect to sheathed insertions, the separate distal tip sections may tend to flare outward and catch or “snag” on the inner wall of the delivery sheath thereby preventing smooth delivery of the catheter to the central vein.
There is a need for improvements to split-tip catheters and new configurations thereof, which enhance the design and further alleviate concerns with regard to typical problems encountered in hemodialysis catheters. There is also a need for new configurations and new methods for insertion of split-tip catheters to overcome problems associated therewith.